Units for picking up spare wheels designed for use in vehicles, and more specifically units designed for picking up or releasing a spare wheel that are arranged below the chassis (or on the underbody) of the vehicle are known in the state of the art.
These units generally comprise a mechanism with a transmission shaft which allows winding or unwinding a cable when the user manipulates the transmission shaft with a tool. The transmission shaft comprises a gear assembly which allows transmitting a torque which the user produces with the tool, and a drum which allows winding or unwinding the cable and to which the torque is transmitted from the gear assembly.
The gear assembly comprises at least one cam having a toothed area, and a hole in which an eccentric shaft operated by the tool of the user is coupled. The toothed area of the cam has one tooth less than the toothed area of the drum where it is coupled or one tooth less than the toothed area of a ring gear of the gear assembly which is intermediate between the cam and the drum. When the rotation is transmitted from the gear assembly to the drum, a wobbling movement occurs in the cam, i.e., the cam swings in time with a back and forth movement caused by the action of the eccentric shaft. This wobbling movement, also known as a pilgrim movement, along with the fact that the toothed area of the cam has one tooth less than the toothed area of the drum, causes the cam to rotate and go forward one tooth of its toothed area into the teeth of the toothed area of the drum or of the ring gear. The torque is thus transmitted, but the cam also rotates, and to limit the rotation the cam comprises a prolongation abutting with an element of the unit for picking up spare wheels. According to the unit type, the stop can directly be one of the casings of the unit, or the prolongation of the cam can comprise a groove in which a bolt of the unit is located, such that the groove of the cam slides during the wobbling movement and is supported on the abutting bolt, thus preventing rotation of the cam.
European Publication No. EP1352871 A2 discloses a unit for picking up spare wheels comprising a gear assembly which allows transmitting a torque, the gear assembly comprising a cam having a wobbling movement as the gear assembly transmits the torque, and at least one stop limiting the travel of the cam during the wobbling movement.